The present invention generally relates a conical helical concept of a spiral combustor scroll within the combustion system of a gas turbine engine. More specifically, the present invention relates to a scroll designed to utilize as much cavity of combustor housing as possible, and largest possible liner by adding an axial shift and an irregular cross sectional shape in the scroll without adversely effecting aerodynamic performance.
A combustor scroll in a turbine engine is used to deliver the exhaust gases of combustion in such a manner as to drive a turbine. A conventional combustor scroll has a spiral spline attached to a cylindrical or elliptical shape with an air inlet at zero degrees while the air exhaust typically discharges radially or axially toward the inner diameter. A material capable of withstanding high temperatures is usually used to fabricate the body through a forming process or cast. The center of the scroll's cross-sectional area, also known as the cross-sectional area centroid, is not allowed to axially cross the center plane of the “B-width”, or combustion exhaust product discharge area. This conventional concept, however, is adequate for only low cycle, low performance and less weight driven engines.
U.S. Pat. No. 3,837,760 discloses a turbine engine that employs an axial type compressor that uses a scroll curvature design to change air particle flow velocities through various vane angle arrangements. See B, D and U in FIG. 8. A multiple component system accelerates the flow to supersonic speeds with a chiefly peripheral discharge and tubular diffuser to receive the supersonic flow.
U.S. Pat. No. 5,266,033 discloses a centrifugal compressor collector in which the radial cross-sectional area of the housing progressively changes. This progressive change is due to the variation of the housing's axial height as shown in FIGS. 3 through 8 of the patent. The axial shift affects only one common side of the rectangular shape, circumferentially around the housing. The axial shift of the cross-sectional area's center of gravity is progressive and remains on one side of the B-width.
U.S. Pat. No. 5,317,865 discloses a turbine engine design that utilizes an inline combustor integral with the turbine scroll to minimize radial height of the engine. The inline combustor/scroll also minimizes the pressure drop of the combustor inlet air by eliminating the turns associated with a reverse flow can style combustor. The combustor is spiral shaped and positioned between the compressor and turbine which allows the direction of flow of air or working gas to remain substantially unchanged from the compressor to the turbine.
As can be seen, new engine designs have resulted in new technical challenges that require an improved turbine scroll shape. Such a turbine scroll must have the ability to accommodate a larger liner than usual due to emergency starting requirements. The liner and scroll must utilize as much cavity in the combustor housing as possible without adversely effecting performance. This allows a smallest possible combustor housing design and therefore reduce the weight of the entire system.